Light emitting device

ABSTRACT

A light emitting device includes a base, a first semiconductor laser element, a second semiconductor laser element, a lens member, and a waveplate. The base has a bottom part. The first semiconductor laser element is disposed on the bottom part of the base. The second semiconductor laser element is disposed on the bottom part of the base. The second semiconductor laser element has a different polarization direction from a polarization direction of the first semiconductor laser element. The lens member is a member into which light beams from the first semiconductor element and the second semiconductor laser element enter. The waveplate is configured to change the polarization direction of light from the first semiconductor laser element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 16/560,310, filed on Sep. 4, 2019. This application claimspriority to Japanese Patent Application No. 2018-166642 filed on Sep. 6,2018, and Japanese Patent Application No. 2019-100022 filed on May 29,2019. The entire disclosures of U.S. patent application Ser. No.16/560,310 and Japanese Patent Application Nos. 2018-166642 and2019-100022 are hereby incorporated herein by reference.

BACKGROUND

The present disclosure relates to a light emitting device.

A light emitting device comprising multiple light emitting elements,such as LEDs or lasers, has been known. In some cases, optical systemsfor various types of light source devices such as projectors, liquidcrystal displays, headlights and the like are designed by incorporatinga plurality of light emitting elements. In designing such opticalsystems, certain conditions related to optical characteristics, such asthe travelling direction of a light beam, the emission region, or thepolarization direction are set.

The use of a lens for collecting, diverging, or collimating lightemitted from a light emitting element has been known. Alternatively, amirror can be provided in the beam path before the light reaches a lens.For example, Japanese Patent Publication No. 2017-212390 discloses aprojector incorporating a light source device including a plurality ofsemiconductor laser elements, a plurality of prisms, and an opticalsystem with which the light beams emitted by the semiconductor laserelements are reflected and are allowed to enter the lenses disposedupwards of the light source device, The beam path lengths reaching thelenses can be increased by interposing light reflecting members, such asmirrors or prisms, in a package having a limited space.

For example, Japanese Patent Publication No. 2017-90799 discloses alaser light source for a display device where the polarizationdirections of a red laser light source, a blue laser light source, and agreen laser light source are aligned.

SUMMARY

As in the case of the light source device disclosed in Japanese PatentPublication No. 2017-212390, the light beam diverges as the beam pathlength is increased by interposing a light reflecting member.

A light emitting device according to one aspect of the presentdisclosure includes a base, a first semiconductor laser element, asecond semiconductor laser element, a lens member, and a waveplate. Thebase has a bottom part. The first semiconductor laser element isdisposed on the bottom part of the base. The second semiconductor laserelement is disposed on the bottom part of the base. The secondsemiconductor laser element has a different polarization direction froma polarization direction of the first semiconductor laser element. Thelens member is a member into which light beams from the firstsemiconductor element and the second semiconductor laser element enter.The waveplate is configured to change the polarization direction oflight from the first semiconductor laser element.

According to the present disclosure, a light emitting device withreduced beam divergence angle can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a light emitting device according to afirst embodiment.

FIG. 2 is a perspective view of the light emitting device according tothe first embodiment viewed in the same angle as in FIG. 1 with aportion of the structure removed.

FIG. 3 is a top view of the light emitting device according to the firstembodiment.

FIG. 4 is a top view of the light emitting device according to the firstembodiment corresponding to FIG. 2 .

FIG. 5 is a cross-sectional view of the light emitting device accordingto the first embodiment taken along line V-V in FIG. 3 .

FIG. 6 is a cross-sectional view of the light emitting device accordingto the first embodiment taken along line VI-VI in FIG. 3 .

FIG. 7 is a schematic diagram showing the major portions of the emittedlight beams from a first semiconductor laser element and a secondsemiconductor laser element of the light emitting device according tothe first embodiment.

FIG. 8 is a diagram illustrating the travelling paths of the rays oflight emitted from a second semiconductor laser element and exiting fromthe lens member according to the light emitting device of the firstembodiment.

FIG. 9 is a diagram illustrating the travelling paths of the rays oflight emitted from a first semiconductor laser element and exiting fromthe lens member according to the light emitting device of the firstembodiment.

FIG. 10 is a diagram illustrating the light reflecting surface of thefirst light reflecting member in the case where the distances to theirradiation points for the central rays from the first and secondsemiconductor laser elements are aligned.

FIG. 11 is a diagram illustrating examples of the conditions met by thelocation of the first semiconductor laser element and the shape of thelight reflecting surface of the first light reflecting member.

FIG. 12 is a perspective view of a light emitting device according to asecond embodiment.

FIG. 13 is a top view of the light emitting device according to thesecond embodiment.

FIG. 14 is a cross-sectional view of the light emitting device accordingto the second embodiment taken along line XIV-XIV in FIG. 12 .

FIG. 15 is a perspective view of a light emitting device according to athird embodiment.

FIG. 16 is a top view of a light emitting device according to the thirdembodiment.

FIG. 17 is a cross-sectional view of the light emitting device accordingto the third embodiment taken along line XVII-XVII in FIG. 16 .

FIG. 18 is a cross-sectional view of the light emitting device accordingto the third embodiment taken along line XVIII-XVIII in FIG. 16 .

FIG. 19 is a cross-sectional view of the light emitting device accordingto the third embodiment taken along line XIX-XIX in FIG. 16 .

FIG. 20 is a perspective view of a light emitting device according to afourth embodiment.

FIG. 21 is a top view of the light emitting device according to thefourth embodiment.

FIG. 22 is a cross-sectional view of the light emitting device accordingto the fourth embodiment taken along line XXII-XXII in FIG. 21 .

FIG. 23 is a perspective view of the light emitting device according tothe fourth embodiment viewed in the same direction as in FIG. 20 with aportion of the structure removed.

FIG. 24 is a perspective view of a light emitting device according to afifth embodiment.

FIG. 25 is a top view of the light emitting device according to thefifth embodiment.

FIG. 26 is a cross-sectional view of the light emitting device accordingto the fifth embodiment taken along line XXVI-XXVI in FIG. 25 .

FIG. 27 is a perspective view of the light emitting device according tothe fifth embodiment viewed in the same direction as in FIG. 24 with aportion of the structure removed.

DESCRIPTION

Certain embodiments of the present invention will be explained belowwith reference to the drawings. However, the embodiments described beloware for giving shape to the technical ideas of the present invention andare not intended to limit the present invention. In the explanationbelow, moreover, the same designations and reference numerals show thesame or similar components for which detailed explanation will beomitted as appropriate. The sizes of and positional relationship betweenthe members might be exaggerated for clarity of explanation.

First Embodiment

FIG. 1 to FIG. 6 are diagrams for illustrating the structure of a lightemitting device 1 according to a first embodiment. FIG. 1 is aperspective view of the light emitting device 1 viewed from the sidefrom which light exits. FIG. 2 is a perspective view of the lightemitting device 1 visualizing the space where the semiconductor laserelements are disposed by removing a portion of constituent members whenviewed in the same direction as in FIG. 1 . FIG. 3 is a top view of thelight emitting device 1 shown in FIG. 1 assuming that the side fromwhich light exits is the upper surface. FIG. 4 is a top view of thelight emitting device 1 shown in FIG. 2 assuming that the side fromwhich light exits is the upper surface. FIG. 5 is a cross-sectional viewof the light emitting device 1 taken along line V-V in FIG. 3 . FIG. 6is a cross-sectional view of the light emitting device 1 taken alongline VI-VI in FIG. 3 . The light emitting device 1, including wires, isshown in FIG. 4 , but the wires are omitted in the other drawings so asto reduce obscurity.

The light emitting device 1 includes constituent elements such as a base10, a single first semiconductor laser element 20, two secondsemiconductor laser elements 30, a submount 40, a first light reflectingmember 50, a second light reflecting member 60, a cover member 70, alens member 80, bonding parts 90, and wires 91. The lens member 80 maybe disposed on another device instead of the light emitting device 1.

A light emitting device may be constructed only with a firstsemiconductor laser element 20 among the first and second semiconductorlaser elements. In the case where there is no second semiconductor laserelement 30, the second light reflecting member 60 does not have to beprovided. A plurality of first semiconductor laser elements 20 may bearranged. Similarly, one or multiple second semiconductor laser elements30 may be arranged. Depending on the material or structure of the base10. a semiconductor laser element can be mounted without a submount 40.

Each constituent element will be explained next.

The base 10 has a bottom part which forms the bottom surface of the base10, and a frame part which forms the lateral surfaces of the base 10.The frame part has inner lateral surfaces IS. The inner lateral surfacesIS and the upper surface US of the bottom part form the base with arecessed structure where the central portion is recessed. Stepped partsST are provided at certain inner surfaces of the frame part. The steppedparts ST may be provided across all inner lateral surfaces. A metal filmis disposed on the upper surface of a stepped part.

The base 10 may be composed of a ceramic as a main material. A metalinstead of ceramic may be used to form the base. Example materials asmain materials for the base 10 include: ceramics such as aluminumnitride, silicon nitride, aluminum oxide, or silicon carbide; metalssuch as copper, aluminum, or iron; and a composite material such ascopper molybdenum, copper diamond, or copper tungsten. Alternatively,the base 10 may be formed by providing the bottom part and the framepart as separate members composed of different main materials, andjoining the bottom part and the frame part together. This, for example,includes employing as a main material different metals for the bottompart and the frame part, or using a bottom part composed of a metal as amain material and a frame part composed of a ceramic as a main material.

The first semiconductor laser element 20 and the second semiconductorlaser elements 30 emit laser beams. The laser beams emitted from thesesemiconductor laser elements are divergent beams, forming an ellipticalfar field pattern (hereinafter referred to as FFP) in a plane parallelto the emission end surface. An FFP is identified by the luminousintensity distribution of a beam irradiated at a plane located at adistance in some degree from and parallel to the emission end surface.The shape of an FFP can be identified as a region where light havingintensity of 1/e² higher relative to the peak intensity value isdistributed. The beam forming an FFP is referred to as the major portionof light.

FIG. 7 is a schematic diagram showing the major portions of the lightbeams emitted from a first semiconductor laser element 20 and a secondsemiconductor laser element 30 of the light emitting device 1. Thediagram shows only a portion of the light emitting device 1 needed forthe explanation. As shown in FIG. 7 , an FFP is elliptical-shaped,greater in length in the stacking direction of active layer-containingsemiconductor layers than the direction perpendicular thereto. In thedescription herein, the divergence of the beam corresponding to themajor axis diameter of the elliptical shape is referred to as divergencein the vertical direction, and the divergence of the beam correspondingto the minor axis diameter is referred to as divergence in the lateraldirection.

In the space into which the major portion of a light beam travels, thehalf value of the angle formed by the rays of light traveling from theemission end surface to both edges of the major diameter of theelliptical shape is referred to as the vertical beam divergence angle,and the half value of the angle formed by the rays of light travelingfrom the emission end surface to both edges of the minor diameter of theelliptical shape is referred to as the lateral beam divergence angle.Based on FIG. 7 , for both the first and second semiconductor laserelements, the vertical beam divergence angle is denoted as θ1/2 and thelateral beam divergence angle θ2/2 . The vertical beam divergence angleis larger than the lateral beam divergence angle for both the first andsecond semiconductor laser elements 20 and 30.

The light emitted from the first semiconductor laser element 20 haslarger vertical beam divergence angle than that of the light emittedfrom the second semiconductor laser element 30. Depending on the beamdivergence angle of the semiconductor laser element employed, in orderto effectively apply the light emitting device 1 of the firstembodiment, it is preferable for the first semiconductor laser element20 and the second semiconductor laser elements 30 to satisfy thecondition such that the vertical beam divergence angle of the lightemitted from the first semiconductor laser element 20 is 10 or moredegrees larger. The difference in the vertical beam divergence angle ofthe laser beams between the first semiconductor laser element 20 and thesecond semiconductor laser elements 30 can be set, for example, to 30degrees at most.

For example, a red light emitting semiconductor laser element isemployed for the first semiconductor laser element 20, and a blue lightemitting semiconductor laser element and a green light emittingsemiconductor laser element are employed for the second semiconductorlaser elements 30. Besides employing semiconductor laser elements ofthese three colors, a different color combination may be employed.

The peak emission wavelength of red light is preferably in the range offrom 605 nm to 750 nm, more preferably in the range of from 610 nm to700 nm. Examples of red light emitting semiconductor laser elementsinclude those including an InAlGaP-based, GaInP-based, GaAs-based, orAlGaAs-based semiconductor. For a semiconductor laser element includingthese semiconductors, output reduction due to heat tends to occur ascompared to a semiconductor laser element including a nitridesemiconductor. Considering this point, it is preferable to provide twoor more waveguide areas, Increasing the waveguide areas can increaseheat dissipation area, thereby attenuating the output reduction of asemiconductor laser element.

The peak emission wavelength of blue light is preferably in the range offrom 420 nm to 494 nm, more preferably in the range of from 440 nm to475 nm. Examples of blue light emitting semiconductor laser elementsinclude those including nitride semiconductors. For nitridesemiconductors, for example, GaN, InGaN, and AlGaN may be used.

The peak emission wavelength of green light is preferably in the rangeof from 495 nm to 570 nm, more preferably in the range of from 510 nm to550 nm. Examples of green light emitting semiconductor laser elementsinclude those including nitride semiconductors. For nitridesemiconductors, for example, GaN, InGaN, and AlGaN can be used.

The submount 40 is constructed as a rectangular parallelepiped. Theshape, however, is not required to be a rectangular parallelepiped. Thesubmount 40 can be formed, for example, with silicon nitride, aluminumnitride, or silicon carbide. The materials that can be used are notrequired to be these. Moreover, a metal film is disposed on a portion ofthe submount 40.

The first and second light reflecting members 50 and 60 each have abottom surface, lateral surfaces substantially perpendicularly extendingfrom the bottom surface, and an upper surface meeting the lateralsurfaces at the opposite side of the bottom surface. A portion of theupper surface is not in parallel to the bottom surface. A portion of theupper surface is in parallel to the bottom surface. A light reflectingsurface for reflecting light is formed at least in the area that is notin parallel with the bottom surface. The light reflecting surface of thefirst light reflecting member 50 and the light reflecting surface of thesecond light reflecting member 60 have different shapes. The firstreflecting member 50 has a concave light reflecting surface, and thesecond reflecting member 60 has a flat light reflecting surface. Thesecond light reflecting member 60 is designed such that the bottomsurface and the flat light reflecting surface form a 45 degree angle.

The first and second light reflecting members 50 and 60 can be formed byusing a heat resistant material as a main material for the exterior anda high reflectance material for the surface of the exterior where thelight reflecting surface is to be provided. For the main material,glass, such as quartz, borosilicate glass (BK7), or the like, metalssuch as aluminum or the like, or Si or the like, can be employed. Forthe light reflecting surface, metals, such as Ag, Al, or the like,dielectric multilayer film, such as Ta₂O₅/SiO₂, TiO₂/SiO₂, Nb₂O₅/SiO₂,or the like, can be employed. The exterior of the first and the secondlight reflecting members 50 and 60 may be formed by using a materialwith high reflectance such as metals while omitting the light reflectingfilm. The light reflecting surfaces of the first and the second lightreflecting members 50 and 60 can be designed to have reflectance of atleast 99% for the peak wavelengths of the laser beams to be reflected.The reflectance can be set to 100% at most or less than 100%.

The cover member 70 is constructed as a rectangular parallelepiped. Thecover member 70, moreover, is light transmissive as a whole. It may havea non-light transmissive area. The shape is not required to be arectangular parallelepiped. The cover member 70 can be formed by usingsapphire as a main material. A metal film is disposed in one area.Sapphire is a material having a relatively high refractive index andrelatively high strength. For the main material, glass or the like, forexample, can be used other than sapphire.

The lens member 80 has three lens parts 82 having a lens shape, and anon-lens part 81. The lens member 80 is structured in the form oflinking the three lens parts 82 on the non-lens part 81. For example, byusing a mold having such a shape, the lens member 80 integrally formingthe non-lens part 81 and the lens parts 82 can be manufactured.Manufacturing such an integrally composed lens part 80 is good in termsof production efficiency.

Alternatively, the lens member 80 may be constructed by separatelypreparing a member shaped as a non-lens part 81 and members shaped aslens parts 82 followed by bonding the lens parts 82 onto the planeformed by the non-lens part 81. For the lens member 80, glass such asBK7, B270, borosilicate glass, or the like can be used.

The flat surface overlapping the surface of the non-lens part 81 onwhich the lens parts 82 are provided is referred to as the interface ofthe lens parts 82 or the non-lens part 81. When the term “interface ofthe lens parts 82” is used, it refers to the surfaces of the lens parts82 overlapping the interface. Even in the case where the lens parts 82and the non-lens part 81 are integrally formed, the regions virtuallyoverlapping the interface can be considered as such. Moreover, in thecase where the lens member 80 has no non-lens part 81, the flat surfaceopposing the surfaces of the lens parts 82 having lens shapes (i.e.,curved surface structures) is considered as the interface of the lensparts 82.

The bonding parts 90 are formed by solidifying a bonding material. It'spreferable to use a UV curable resin for the bonding parts 90. A UVcurable resin can secure the lens member 80 at a given position becauseit can harden in a relatively short time without involving heating.

The light emitting device 1 manufactured by using these constituentelements will be explained next.

A first semiconductor laser element 20 and two second semiconductorlaser elements 30 are disposed via a submount 40 on the upper surface USof the bottom part, which is the bottom surface of the base 10. In thecase where a submount 40 is not interposed, the first and secondsemiconductor laser elements are directly disposed on the upper surfaceUS of the bottom part. In the light emitting device 1. a red firstsemiconductor laser element 20, a blue second semiconductor laserelement 30. and a green second semiconductor laser element 30 aredisposed.

In the light emitting device 1, the blue light emitting secondsemiconductor laser element 30 is positioned in the center which isinterposed by the red light emitting first semiconductor laser element20 and the green light emitting second semiconductor laser element 30.This takes into consideration the fact that the red light emitting firstsemiconductor laser element 20 is inferior to the others in terms ofoptical output under the heated condition. This also takes intoconsideration the fact that the amount of heat generated by the bluelight emitting second semiconductor laser element 30 is smaller thanthat of the green light emitting second semiconductor laser element 30.In other words, considering such thermal characteristics, the one havingthe best characteristics among the three semiconductor laser elements ispreferably positioned in the middle.

Furthermore, a single first light reflecting member 50 and a singlesecond light reflecting member 60 are disposed on the upper surface USof the bottom part. The upper surface US of the bottom part is bonded tothe bottom surfaces of the first and second light reflecting members.The first and second light reflecting members are disposed so that themajor portion of the light beam emitted from the first semiconductorlaser element 20 irradiates the light reflecting surface of the firstlight reflecting member 50, and the major portions of the light beamsemitted from the second semiconductor laser elements 30 irradiate thesecond light reflecting member 60.

Allowing for reflection using the light reflecting members can increasethe beam path lengths as compared to cases where no light reflectingmember is provided. The effect of mounting misalignment between thelight reflecting members and the semiconductor laser elements can bereduced when the beam path lengths are greater. Two second lightreflecting members 60 may be provided to individually correspond to twosecond semiconductor laser elements 30 instead of a single second lightreflecting member 60 corresponding to two second semiconductor laserelements 30.

The frame part of the base 10 surrounds the first and secondsemiconductor laser elements 20 and 30 disposed on the upper surface USof the bottom part, the submount 40, and the first and second lightreflecting members 50 and 60. Accordingly, these constituent elementsare arranged on the upper surface US of the bottom part inward of theframe part. Each of the wires 91 at one end are connected to the metalfilm disposed on the upper surfaces of the stepped parts ST of the framepart. Each of the wires 91 at the other end are connected to the firstand second semiconductor laser elements. This can electrically connectthe first and second semiconductor laser elements 20 and 30 to a powersupply externally provided.

The stepped parts ST are not provided in certain areas of the innerlateral surfaces IS of the frame part of the base 10. These areas arelocated at the lateral surface of the base 10 opposing the lateralsurface of the first semiconductor laser element 20 close to the firstlight reflecting member 50, and the lateral surface of the base 10opposing the lateral surface of the first light reflecting member 50closet to the first semiconductor laser element 20. If a stepped part STwere positioned at the lateral surface of the base 10 which is on theopposite side of the lateral surface close to the first semiconductorlaser 20, the wire 91 connected to the first semiconductor laser element20 would span over the first light reflecting member 50. That is why nostepped part ST for the purpose of establishing an electrical connectionis formed there. By not forming stepped parts ST in certain areas, asmaller light emitting device 1 can be produced.

On the upper surface of the submount 40, three semiconductor laserelements are disposed. The submount 40 may be disposed for the first andsecond semiconductor laser elements 20 and 30 on a one-to-one basis. Thebottom surface of the submount 40 is bonded to the bottom pail of thebase 10, and the upper surface of the submount is bonded to thesemiconductor laser elements. The semiconductor laser elements arebonded to the metal film disposed on the upper surface of the submount40 via a conductive bonding material such as Au—Sn or the like.

From a heat dissipation perspective, using a material having higherthermal conductivity than the bottom part of the base 10 allows thesubmount 40 to achieve a more enhanced effect as a heat dissipater. Forexample, in the case of employing a material which includes a nitridesemiconductor for the semiconductor laser elements and aluminum nitrideas a main material for the base 10, aluminum nitride or silicon carbidemay be used for the submount 40. In the case of using aluminum nitridefor both the base 10 and the submount 40, aluminum nitride having higherconductivity than the aluminum nitride used for the base 10 may beemployed for the submount 40.

Furthermore, the shape of the submount 40 is designed so that theheights of the semiconductor laser elements 20 and 30 from the bottompart are the same. Moreover, it is designed so that the distance betweenthe submount 40 under the first semiconductor laser 20 and the firstlight reflecting member 50 is the same as the distance between thesubmount 40 under the second semiconductor lasers 30 and the secondlight reflecting member 60. A manufacturing tolerance may occur due to acomponent tolerance, position tolerance, or the like, even ifmanufactured with the same design. When heights, lengths, or positionsin the light emitting device 1 are described as being the same, thesetolerances in permissible ranges are included. It's allowed that theseheights and distances do not have to be the same.

The distance between the emission end surface of the first semiconductorlaser element 20 and the first light reflecting member 50 is designed tobe the same as the distance between the emission end surfaces of thesecond semiconductor laser elements 30 and the second light reflectingmember 60. The emission end surfaces of the first and secondsemiconductor laser elements are designed to be located in the sameplane. That is, they are designed using two virtual parallel planes suchthat the emission end surfaces of the first and second semiconductorlaser elements are located in one of the two virtual parallel planes,and the lateral surface of the first light reflecting member 50 closestto the first semiconductor laser element 20 and the lateral surface ofthe second light reflecting member 60 closest to the secondsemiconductor laser elements 30 are located in the other virtualparallel plane.

The cover member 70 is bonded to the frame part at the upper surface ofthe base 10 which opposes the bottom surface (first surface) of thecover member 70, covering the frame formed by the inner surfaces IS ofthe frame part. A metal film is disposed in the area of the lowersurface of the cover member 70 that is to be joined with the base 10,and the cover member 70 is secured to the position via Au-Sn or thelike. In the case of covering the frame using a rectangularparallelepiped cover member 70, the height from the bottom surface ofthe base 10 to the upper surface of the frame is higher than the heightsof the first and second semiconductor laser elements 20 and 30 from thebottom surface of the base 10, and higher than the heights of the firstand second light reflecting members 50 and 60.

The base 10 and the cover member 70 after being joined together make theclosed space hermetically sealed. Hermetically sealing the space in thismanner can attenuate that the dust, such as organic matter or the likeis collected at the emission end surfaces of the first and secondsemiconductor laser elements.

The light reflected by the light reflecting surfaces of the first andsecond light reflecting members 50 and 60 enters the cover member 70,The cover member 70 is designed to have a light transmissive regionthrough which the reflected light enters and is output so that thereflected light of at least the major portion of the light passesthrough the cover member 70 and is output from the upper surface. In thepresent disclosure, being light transmissive means a transmittance of atleast 80%. In other words, the major portions of the light beamsreflected by the light reflecting surfaces pass through the cover member70 which is transmissive for the wavelength ranges of the light beamsfrom the first and second semiconductor laser elements 20 and 30, andare output from the hermetically sealed space.

The higher the refractive index of the material configuring the regionof the cover member 70 where light beams pass, the more effective it isin attenuating beam divergence. For example, the cover member 70 ispreferably constructed with sapphire at least in the regions throughwhich the major portion of the light beam from the first semiconductorlaser element reflected by the light reflecting surface of the firstlight reflecting member passes through, and which the major portion ofthe light beam from the second semiconductor laser element reflected bythe light reflecting surface of the second light reflecting memberpasses through.

The bonding parts 90 are formed in the regions of the upper surface(second surface) of the cover member 70 where the cover member 70 isbonded to the lens member 80. The bonding parts 90 are formed betweenthe cover member 70 and the lens member 80 by applying an adhesivematerial in the bonding portion of the upper surface of the cover member70, placing the lower surface of the lens member 80 thereto, andhardening the adhesive material. The bonding parts 90 are formed to acertain thickness so that the cover member 70 does not contact the lensmember 80. The thickness is designed by considering the position andcomponent tolerances. This enables bonding of the lens member 80 to thecover member 70 upon adjusting the position and height of the lensmember 80 in the event of a deviation in the position of the lightpassing through the cover member 70 attributable to positional deviationof the semiconductor laser elements and the light reflecting membersmounted on the base 10.

The bonding parts 90, moreover, are not disposed across the entire uppersurface of the cover member 70 or the entire lower surface of the lensmember 80. but are disposed so as not to interfere with the paths of thelight beams emitted from the first and second semiconductor laserelements 20 and 30. Accordingly, the bonding parts 90 are not formed ona region of the lower surface of the lens member 80 corresponding to theregions where the lens parts 82 of the lens member 80 are formed, butare formed in the outer peripheral regions of the lens member 80.

The lens member 80 is bonded to the cover member 70 via the bondingparts 90 on the cover member 70. The lens member 80 is positioned sothat the lens parts 82 of the lens member 80 are located on the surfaceopposing the surface that is bonded to the cover member 70. The threelens parts 82 of the lens member 80 are positioned to individuallycorrespond to the three semiconductor laser elements arranged on thebottom part.

That is, the upper surfaces of the three lens parts 82 are the surfacesfrom which the beams from the three semiconductor laser elementsentering the lens member 80 are output. The major portion of the lightbeam emitted from the first semiconductor laser element 20 is reflectedby the light reflecting surface of the first light reflecting member 50,enters the lens member 80 through the cover member 70, passes through afirst lens part 83, which is one of the three lens parts 82, and isoutput from the lens member 80.

The major portion of the light beam emitted from one of the two secondsemiconductor laser elements 30 is reflected by the light reflectingsurface of the second light reflecting member 60, enters the lens member80 through the cover member 70, passes through a second lens part 84which is one of the three lens parts 82 different from the first lenspart 83, and is output from the lens member 80.

The major portion of the light beam emitted from the other secondsemiconductor laser element 30 is reflected by the light reflectingsurface of the second light reflecting member 60 enters the lens member80 through the cover member 70, passes through a third lens part 85which is the remaining one of the three lens parts 82, and is outputfrom the lens member 80.

As described above, the lens parts 82 are formed so that each lens part82 corresponds to a semiconductor laser element. Accordingly, dependingon the number of semiconductor laser elements provided in the lightemitting device 1, the number of lens parts 82 to be formed can vary.For example, in the case where a light emitting device 1 is providedwith only one semiconductor laser element, the lens member 80 can have asingle lens part 82. That is, the lens member can be provided with asingle or multiple lens parts 82.

The lens shape of each lens part 82 is designed so that the light beamfrom the corresponding semiconductor laser element is collimated when itis output. In the light emitting device 1, the first to third lens parts83 to 85 have different lens shapes, but this indicates that a pluralityof lens parts 82 can have the same lens shape. A lens shape may bedesigned to control the travelling direction of light for the purpose ofcollecting light, or the like, other than collimating light.

In the case where the non-lens part 81 and each of the first to thirdlens parts are separately prepared for the lens member 80, the non-lenspart 81 may be bonded onto the cover member 70 using an adhesive,followed by disposing and bonding each lens part 82 on the upper surfaceof the non-lens part 81. In this case, the positions of the lens parts82 can be determined based on the results of measuring the positions andtravelling directions of the light beams from the first and secondsemiconductor laser elements being output from the non-lens part 81.

How the paths of the light beams emitted from the semiconductor laserelements in the light emitting device 1 constructed as above arecontrolled will be explained next. FIG. 8 , based on the cross-sectionalview in FIG. 5 , is a diagram illustrating the paths of the rays oflight beam from the second semiconductor laser element 30 being outputfrom the lens member 80.

FIG. 9 , based on the cross-sectional view in FIG. 6 , is a diagramillustrating the paths of the rays of light from the first semiconductorlaser element 20 being output from the lens member 80.

In the present embodiment, with respect to each of the first and secondsemiconductor laser elements 20 and 30, the ray of light in the majorportion of the light beam emitted from the semiconductor laser elementthat irradiates the light reflecting surface at the shortest distanceposition from the emission end surface of the semiconductor laserelement is referred to as the lower end ray. The ray of light in themajor portion of the light beam emitted from the semiconductor laserelement that irradiates the light reflecting surface at the longestdistance position from the emission end surface of the semiconductorlaser element is referred to as the upper end ray. The ray of lightadvancing in the direction perpendicular to the emission end surface ofeach semiconductor laser element, in other words, the ray of lighttraveling along the optical axis, is referred to as the central ray.Moreover, the angle formed by the straight line in the travellingdirection of the upper end ray and the straight line in the travellingdirection of the lower end ray is referred to as the angle formed by theupper end ray and the lower end ray.

Using the example shown in FIG. 7 , in the light beam emitted from asemiconductor laser element forming an elliptical FFP, the ray of lightpassing the end of the major diameter of the ellipse closer to the base10 is the lower end ray, and the ray of light passing the other endcloser to the cover member 70 is the upper end ray.

The ray of light travelling in the center of the ellipse is the centralray. In the case where some of the rays of the entire light in thedirection from the upper end to the lower ends forming an FFP do notirradiate the light reflecting surface, the rays of light at both endsof the major diameter of the ellipse are not aligned with the upper andlower end rays.

In FIG. 7 , the position where the upper end ray irradiates the lightreflecting surface is denoted as UP, and the position where the lowerend ray irradiates the light reflecting surface is denoted as LP. Theposition where the central ray from the first semiconductor laserelement 20 irradiating the light reflecting surface of the first lightreflecting member 50 is denoted as CP1, and the position where thecentral ray from the second semiconductor laser element 30 irradiatingthe light reflecting surface of the second light reflecting member 60 isdenoted as CP2.

Furthermore, the region of a constituent element of the light emittingdevice 1 irradiated by the light passing through the major diameter ofan ellipse is referred to as the region corresponding to the majordiameter of the light in the constituent element.

For example, the region of the light reflecting surface of the firstlight reflecting member 50 irradiated by the light from the firstsemiconductor laser element 20 passing through the major diameter of anelliptical FFP will be referred to as, for example, the regioncorresponding to the major diameter of the light beam emitted from thefirst semiconductor laser element 20 in the light reflecting surface ofthe first light reflecting member 50. Accordingly, what is referred toas a region here includes a line-like region that can be a straight orcurved line-like region depending on the shape of the constituentelement.

A region corresponding to the major diameter can similarly be identifiedin the constituent elements where light enters, such as the cover member70, the lens member 80, or the lens parts 82 of the lens member 80, inaddition to the first and second light reflecting members 50 and 60. Inthe case where the region corresponding to the major diameter of lightin a constituent element is a straight line, the direction parallel tothe straight line is referred to as the direction corresponding to themajor diameter of light in the constituent element. A similar expressionapplies to the minor diameter by replacing the major diameter with theminor diameter.

In FIG, 8 and FIG. 9 , the paths of the rays of light from thesemiconductor laser elements being output from the lens member 80 areindicated by dotted lines. The three dotted lines in FIG. 8 show thepaths of the upper end ray, the central ray, and the lower end rayemitted from the second semiconductor laser element 30. The three dottedlines in FIG. 9 show the paths of the upper end ray, the central ray,and the lower end ray emitted from the first semiconductor laser element20. FIG. 9 also shows an auxiliary line L which is a straight lineparallel to the travelling direction of the central ray emitted from thesecond semiconductor laser element 30 after being reflected by the lightreflecting surface of the second light reflecting member 60 and passingthe irradiation point CP1 of the central ray emitted from the firstsemiconductor laser element 20.

In the light emitting device 1, the light beams emitted from the firstand second semiconductor laser elements are reflected by the first andsecond light reflecting members before entering the cover member 70 fromthe hermetically sealed space. The light beams passing through the covermember 70 pass through the space between the cover member 70 and thelens member 80 before entering the lens member 80. The light enteringthe lens member 80 passes through the lens parts 82 to exit from thelight emitting device 1.

The light reflecting surface of the first light reflecting member 50narrows the divergence in the vertical direction of the light from thefirst semiconductor laser element 20. In other words, the lightreflecting surface reflects the light emitted from the firstsemiconductor laser element 20 such that a beam divergence angle of thereflected light is smaller than a beam divergence angle of the lightirradiating the light reflecting surface with respect to the verticaldirection of the light beam.

In the present disclosure, the angle formed by the upper end ray and thelower end ray emitted from the emission end surface of the firstsemiconductor laser element 20 reaching the light reflecting surface isreferred to as the beam divergence angle of the light irradiating thelight reflecting surface in the vertical direction. The angle formed bythe upper end ray and the lower end ray reflected by and travelling fromthe light reflecting surface is referred to as the beam divergence angleof the reflected light in the vertical direction.

In the present disclosure, the angle formed by the upper end ray and thelower end ray includes the central ray.

On the other hand, because the light reflecting surface of the secondlight reflecting member 60 is flat, the angle formed by the upper endray and the lower end ray remains unchanged for the light reaching thelight reflecting surface (the beam divergence angle of the lightirradiating the light reflecting surface in the vertical direction) andthe light travelling from the light reflecting surface (the beamdivergence angle of the reflected light in the vertical direction).

The light reflecting surface of the first light reflecting member 50narrows the divergence of the light emitted from the first semiconductorlaser element 20 in the vertical direction, but does not collimate thelight. That is, it is designed so that the beam divergence angle of thereflected light in the vertical direction will not become zero degrees.As shown in FIG. 9 , furthermore, the light reflecting surface of thefirst light reflecting member 50 in the light emitting device 1 isdesigned so as to allow the reflected light to be divergent to someextent.

Divergent light is defined as that satisfying the relationship such thatthe distance between two different points of the same beam path lengthpassed by the rays of light from a semiconductor laser increases as thebeam path length increases. Accordingly, in the light emitting device 1,this relationship is satisfied at least before the light beam reflectedby a light reflecting surface enters the cover member 70. For example,in the case where the light beam from a focus is reflected by ahyperboloidal reflecting surface, the reflected light is divergent.

If designed to collimate reflected light, the light entering the lensmember 80 would already be collimated, making the first lens part 83unnecessary. In the event that the mounting positions or the like of thefirst semiconductor laser element 20 and the first light reflectingmember 50 deviate from the design values, the impact of such a deviationcould not be compensated for even if the mounting position or the heightof the lens member 80 were adjusted. In contrast, designing the shape ofthe light reflecting surface of the first light reflecting member 50such that the light is divergent while reducing the beam divergencethrough reflection allows the first lens part 83 of the lens member 80to adjust the output light.

The shape of the light reflecting surface of the first light reflectingmember 50 may be configured such that the reflected light is convergentinstead of divergent. Convergent light is defined as that satisfying therelationship such that the distance between two different points of thesame beam path length passed by the rays of light decreases as the beampath length increases, For example, in the case where the light beamfrom a focus is reflected by an elliptical reflecting surface, thereflected light is convergent light. In the case where the light beamfrom a focus are reflected by a paraboloidal reflecting surface, thereflected light is collimated.

In the light emitting device 1, the beams from the second semiconductorlaser elements 30 are divergent until they exit from the lens member 80,thus the beam from the first semiconductor laser element 20 is made tobe consistent therewith. This can reduce the impact of a mountingmisalignment. Furthermore, the curvature of the light reflecting surfaceof the first light reflecting member 50 can be reduced when designed todiverge light as compared to converging light. The impact of a mountingmisalignment can be reduced when the curvature is smaller.

For example, in the light emitting device 1, the shape of the curvedlight reflecting surface can be designed so as to narrow the angleformed by the upper end ray and the lower end ray to the range that isgreater than zero degrees, but 20 degrees at most, with respect to thesemiconductor laser beam having the vertical beam divergence angle of 55degrees or greater.

The light reflecting surface of the first light reflecting member 50 isdesigned to have a cylindrical surface so as to be curved in thedirection corresponding to the major diameter of the beam from the firstsemiconductor laser element 20 and be straight in the directioncorresponding to the minor diameter of the beam. For this reason,component and position tolerances for the first semiconductor laserelement 20 and the first light reflecting member 50 in the direction ofthe minor diameter do not affect the travelling direction of the lightreflected by the light reflecting surface in the direction of the majordiameter.

The light reflecting surface of the first light reflecting member 50that is a cylindrical surface does not change the beam divergence angleof the reflected light in the lateral direction. Such a shape can beconsidered as one focusing on the control accuracy of the beamdivergence in the vertical direction rather than controlling the beamdivergence in the lateral direction because the first and secondsemiconductor laser elements in the light emitting device 1 emit laserbeams forming an FFP with smaller the lateral beam divergence angle thanthe vertical beam divergence angle.

The light reflecting surface of the first light reflecting member 50 maybe designed to narrow not only the beam divergence in the verticaldirection, but also the beam divergence in the lateral direction. Forexample, it can be shaped to also have a curvature in the lateraldirection, such as a spherical surface or a toroidal surface, instead ofa cylindrical surface.

The distance from the emission end surface of the first semiconductorlaser element 20 to the position CPI on the light reflecting surface ofthe first light reflecting member 50 where the central ray irradiates isgreater than the distance from the emission end surface of the secondsemiconductor laser element 30 to the position CP2 on the lightreflecting surface of the second light reflecting member 60 where thecentral ray of the second semiconductor laser element 30 irradiates.That is, the central ray of the first semiconductor laser element 20 isreflected at a more distant position.

FIG. 10 is a diagram showing the light reflecting surface of the firstlight reflecting member 999 in the case of matching the distance to theirradiation point of the central ray of the first semiconductor laserelement 20 to the distance to the position CP2 irradiated by the centralray of the second semiconductor laser element 30. The broken line is avirtual line indicating the shape of the light reflecting surface of thefirst light reflecting member 50. As shown in FIG. 10 , the lightreflecting surface is smaller in the first light reflecting member 999with the matched distance to the CP2 than that of the first lightreflecting member 50.

Accordingly, when the vertical beam divergence angle is large, a largeramount of light can be irradiated at the light reflecting surface bypositioning the CPI farther than the CP2 compared to a case where theCPI is positioned at the same distance as the CP2.

The light reflecting surface of the first light reflecting member 50 isdesigned to reflect the central ray from the first semiconductor laserelement 20 in the direction that forms an acute angle with the opticalaxis, not perpendicular to the optical axis. On the other hand, thelight reflecting surface of the second light reflecting member 60 isdesigned to reflect the central ray from the second semiconductor laserelement 30 in the direction perpendicular to the optical axis. Moreover,when a reflection angle is defined as an angle that is formed by thedirection of the central ray incident on the light reflecting surfaceand the direction of the reflected light entering the cover member 70and that does not span over the light reflecting member, the reflectionangle at the light reflecting surface of the first light reflectingmember 50 for the first semiconductor laser element 20 is smaller thanthe reflection angle at the light reflecting surface of the second lightreflecting member 60 for the second semiconductor laser element 30.

This takes into consideration the fact that the central ray of the firstsemiconductor laser element 20 is reflected at a position farther fromthe emission end surface in terms of the positional relationship betweenthe CP1 and the CP2 described above. FIG. 11 shows an example of aspecific layout in the case of making the region corresponding to themajor diameter of light in the light reflecting surface of the firstlight reflecting member 50 a hyperbola. Assuming that the vertex of thehyperbola which forms the light reflecting surface is VX, the focuscloser to the hyperbola is F1, and the other focus is F2, the emissionposition at the emission end surface of the first semiconductor laserelement 20 is set at the focus F1. By setting the angle formed by thesegment connecting the focus F1 with the position CP1 and the segmentconnecting the focus F2 with the position CP1 to that exceeding 90degrees, the central ray can be reflected to form an acute angle withthe optical axis as described above. The angle formed by the segmentconnecting the position CP1 with the focus F1 and the segment connectingthe vertex VX with the focus F1 is smaller than 90 degrees.

The first to third lens parts are linked so as to have the same lenswidth LW, and the same center of the lens width LW, in the directioncorresponding to the major diameters of light at the interface of thelens parts 82. In this manner, each lens part 82 can output collimatedlight having the same width in the direction corresponding to the majordiameter of light at the interface of the lens part 82.

This can also align the exiting positions of the collimated beams in thedirection corresponding to the major diameter of light at the interfacefor the lens parts 82.

The first to third lens parts are linked as described above, thus thecentral ray of the first semiconductor laser element 20 and the centralrays of the second semiconductor laser elements 30 can be reflected bythe light reflecting surfaces at the same angle. This can create thedistance difference at the lens member 80 equivalent to the distancedifference created at the light reflecting surfaces.

Accordingly, allowing the central ray of the first semiconductor laserelement 20 to be reflected at a smaller angle as compared to the centralray of the second semiconductor laser elements 30 as described above canreduce the misalignment of the regions corresponding to the majordiameters of the light beams emitted from the lens member 80 between thelight beams emitted from the first semiconductor laser element 20 andthe second semiconductor laser elements 30.

Specifically, with respect to the direction corresponding to the majordiameters of the beams at the interface for the lens parts 82, theshapes of the light reflecting surfaces arc designed such that thedistance between the output point of the central ray of the firstsemiconductor laser element 20 and the output point of the central rayof a second semiconductor laser element 30 exiting the lens parts 82 issmaller than the distance between the irradiation point of the centralray of the first semiconductor laser element 20 and the irradiationpoint of the central ray of the second semiconductor laser element 30 inthe light reflecting surfaces.

Moreover, the light reflecting surface of the first light reflectingmember 50 is preferably designed to have a shape to control thetravelling direction of the reflected light so as to maximize the amountof the light output through the first lens part 83, in other words,minimize the amount of the light not passing through the first lens part83.

It is more preferably designed such that the lower end ray and the upperend ray from the first semiconductor laser element 20 fit in the lenswidth LW of the first lens part 83 at the interface of the first lenspart 83 in the direction corresponding to the major diameter of thelight at the interface of the first lens parts 83.

In other words, the lower end ray and the upper end ray from the firstsemiconductor laser element 20 preferably pass through the interface ofthe first lens part 83. The lower end rays and the upper end rays of thefirst semiconductor laser element 30 pass through the lens part 83 toexit. The same applies to the lower end rays and the upper end rays ofthe two second semiconductor laser elements 30 passing through thecorresponding second and third lens parts 84 and 85.

As described above, the light emitting device 1 according to the firstembodiment can reduce the spreading of the exiting light by reflectingthe light beam from the first semiconductor laser element 20 using thefirst light reflecting member 50 and allowing the light to exit throughthe first lens part 83 of the lens member 80. This can narrow the beamthat passes through the lens part 82, thereby allowing a smaller lenspart 82 to control the travelling direction of light.

The light emitting device 1 according to the first embodiment is usefulin the case of outputting collimated light while collecting the light ina small region. The light emitting device 1 according to the firstembodiment can be utilized, for example, in the case of outputtingcollimated light so as to collect as much light as possible in acircular region having a diameter of a few millimeters.

Particularly, a light emitting device 1 according to the firstembodiment, is capable of allowing 90% or more of the major portion ofthe light emitted from the first semiconductor laser element 20 having avertical beam divergence angle in the range of from 55 degrees to 75degrees to pass through the first lens part 83 having a lens width LW inthe direction corresponding to the major diameter of light in the rangeof from 1.0 mm to 2.0 mm.

Second Embodiment

A light emitting device 2 according to a second embodiment will beexplained next. It is similar to the light emitting device 1 accordingto the first embodiment in terms of having the constituent elements suchas a base, a single first semiconductor laser element, two secondsemiconductor laser elements, a submount, a first light reflectingmember, a second light reflecting member, a cover member, a lens member,bonding parts, and wires. The differences from the first embodimentinclude the shape of the lens member 280 and the position of the surfacewhere the lens part 282 is disposed. FIG. 12 is a perspective view ofthe light emitting device 2 viewed from the side from which light exits.FIG. 13 is a top view of the light emitting device 2 shown in FIG. 12assuming that the side from which light exits is the upper surface. FIG.14 is a cross-sectional view of the light emitting device 2 taken alongline XIV-XIV in FIG. 12 ,

The lens member 280 will be explained next.

The lens member 280 has three lens parts 282 each having a lens shape,and a non-lens part 281. The same shapes as those in the firstembodiment can be employed for the three lens parts 282. The non-lenspart 281 in the light emitting device 2 is a recessed structuredifferent from that in the first embodiment which is a rectangularparallelepiped. The three lens parts 282 are disposed in the recess ofthe non-lens part 281.

The heights of the three lens parts 282 disposed in the recess from theinterface are equal to the uppermost surface of the recessed structurefrom the interface. Being “equal” here includes a difference of up to0.1 mm.

There may be a difference of more than 0.1 mm in the case where theheight of a lens part 282 is smaller than the height of the uppermostsurface of the recessed structure. That is, the heights of the threelens parts 282 from the interface are designed to be equal to or smallerthan the height of the uppermost surface of the recessed structure fromthe interface. The heights of the lens parts 282 can be larger than theheight of the uppermost surface of the recessed structure with anadjustment made by increasing the thickness of the bonding parts 90.

How the lens member 280 is installed in the light emitting device 2 willbe explained next.

In the light emitting device 2, the lens member 280 is disposed so thatthe three lens parts 282 are disposed on the side that is closer to theupper surface of the cover member 70 so that the lens parts 282 face thecover member 70. Accordingly, the upper surfaces (i.e., lens surfaces)of the three lens parts 282 face down relative to the lens member 280disposed above the base.The uppermost surface of the recessed structure of the lens member 280and the upper surface of the cover member 70 are joined together via anadhesive, which forms bonding parts 90. Assuming that the recessed sideof the non-lens member 281 as the upper surface side and the opposingflat surface as the lower surface side, the lens member 280 is placedupside down such that the lower flat surface is located on the uppersurface side of the light emitting device.

The three lens parts 282 are designed so as not to extend beyond theupper surface of the recessed non-lens part 281 as described above inorder to avoid contact with the cover member 70. Designing them tocontact the cover member 70 makes it difficult to adjust the positionsand heights when and after bonding the lens member 280 to the covermember 70.

The three lens parts 282 of the lens member 280 are positioned toindividually correspond to the three semiconductor laser elementsdisposed on the bottom part. That is, the upper surfaces (i.e., lenssurfaces) of the three lens parts 282 are the incident surfaces throughwhich the light beams emitted from the three semiconductor laserelements enter the lens member 280.

The first lens part 283, the second lens part 284, and the third lenspart 285 are arranged to respectively collimate the light from the firstsemiconductor laser element 20, one of the two second semiconductorlaser elements 30, and the other second semiconductor laser element 30,which is also in common with the light emitting device 1 of the firstembodiment. Unlike the light emitting device 1 of the first embodimentin which the first to the third lens parts are disposed on the surfaceof the non-lens part 281 on the upper surface side of the light emittingdevice 1, they are disposed on the opposite surface of the non-lens partwithout changing the positions when viewed from above.

In the light emitting device 2 according to the second embodimentconstructed as above, the beam path lengths until the light beams enterthe lens parts 282 of the lens member 280 are smaller than those of thelight emitting device 1 according to the first embodiment. The lightbeams entering the lens parts 282 are collimated, pass through the lensmember 280, and exit from the non-lens part 281. A light beam reflectedby a light reflecting surface of the light reflecting member isdivergent, thus the smaller the beam path length, the smaller thedivergence results. That is, the light emitting device 2 according tothe second embodiment can attenuate the spreading of light beams passingthrough the lens parts as compared to the light emitting device 1according to the first embodiment.

The first lens part 283 for the first semiconductor laser element 20which has larger beam divergence angle than the second semiconductorlaser elements 30 may be disposed on the surface of the lens member 280closer to the cover member 70 while positioning the second and thirdlens parts on the surface of the lens member 280 opposing the surfacecloser to the cover member 70.

Third Embodiment

A light emitting device 3 according to a third embodiment will beexplained next. FIG. 15 is a perspective view of the light emittingdevice 3 viewed from the side from which light exits. FIG. 16 is a topview of the light emitting device 3 in FIG. 15 assuming that the sidefrom which light exits is the upper surface. FIG. 17 is across-sectional view of the light emitting device 3 taken along lineXVII-XVII in FIG. 16 . FIG. 18 is a cross-sectional view of the lightemitting device 3 taken along line in FIG. 16 . FIG. 19 iscross-sectional view of the light emitting device 3 taken along lineXIX-XIX in FIG. 16 . The light emitting device 3 according to the thirdembodiment differs from the light emitting device 2 of the secondembodiment in that it additionally includes a waveplate 300. For thewaveplate 300, a half waveplate which changes the polarization directionof light by 90 degrees can be used.

The prior art, for example, Japanese Patent Publication No. 2017-212390,fails to address a light emitting device incorporating multiple lightemitting elements having different polarization directions. On the otherhand, the light emitting device 3 of the third embodiment can outputlight beams with the same polarization direction even though a pluralityof light emitting elements emit light beams with different polarizationdirections.

The waveplate 300, moreover, has a flat plate shape. The waveplate 300is a rectangle in a top view, but it does not have to be a rectangle,and for example, has a shape which is elongated in one direction such asan ellipse.

In the light emitting device 3, the waveplate 300 is provided in orderto change the polarization direction of the light beam emitted from thefirst semiconductor laser element 20. Accordingly, the waveplate 300 ispositioned in the region of the surface of the lens member 280 opposingthe recessed surface where the first lens part 283 is disposed throughwhich the light from the first semiconductor laser element 20 enteringthe first lens part 283 passes.

The light emitted from the first semiconductor laser element 20 exitsfrom the light emitting device 3 after exiting from the lens member 280and passing through the waveplate 300.

The lower surface of the waveplate 300 is bonded to the surface of thelens member 280 opposing the recessed surface where the first lens part283 is disposed. Accordingly, in the light emitting device 3, thewaveplate 300 is disposed above the lens member 280. In a top view, thelength of the long sides of the waveplate 300 is closer to the length ofthe long sides than that of the short sides of the first lens part 283.In the light emitting device 3, the waveplate 300 is disposed byaligning the long sides of the waveplate 300 with the long sides of thefirst lens part 283.

The waveplate 300, moreover, is disposed in the position that covers thefirst lens part 283 in a top view. The waveplate 300 is disposed in theposition and region covering the first lens part 283, but not coveringthe other lens parts, on a top view. Specifically, in the light emittingdevice 3, it is not positioned in the position covering the second lenspart 284 or the third lens part 285 in a top view.

That is, the waveplate is not positioned in the paths of the beams fromthe semiconductor laser elements used as a reference to align thepolarization direction, but the waveplate is positioned in the path ofthe beam from the semiconductor laser element misaligned with thereference polarization direction for the purpose of aligning thepolarization direction.

The long-side length of the waveplate 300 in a top view is the same as,or greater than, the long-side length of the first lens part 283.Preferably, the long-side length is the same as, or smaller than, thelength of the lens member 280 along the long sides of the first lenspart 283. This allows the waveplate 300 to be disposed withoutprojecting from the lens part 280. If the waveplate 300 projects fromthe lens part, a projected portion might be caught on something, whichcould cause the detachment of the waveplate 300.

The short-side length of the waveplate 300 is the same as, or greaterthan, the short-side length of the first lens part 283 in a top view.Preferably, it does not extend beyond the outer surface of the lensmember 280 at the end in the direction approaching from the second lenspart 283 to the first lens part 283 along the short sides of the firstlens part 283, which is the direction extending in the short-side lengthof the first lens part 283. This allows the waveplate 300 to be disposedwithout projecting from the lens member 280 in a top view.

More preferably, it does not extend beyond the inner lateral surface ofthe recess of the lens member 280 at the end in the directionapproaching form the second lens part 284 to the first lens member 283along the short sides of the first lens part 283 in a top view, which isthe direction extending in the short-side length of the first lens part283. This allows the waveplate 300 to control the polarization directionof light without becoming too large in size.

The waveplate 300 is bonded to the lens member 280. A light transmissiveresin adhesive, for example, can be used to bond the waveplate. Anon-light transmissive adhesive can be used, but in this case theadhesive is preferably disposed in the areas other than the regionthrough which light passes, so as not to interfere with the passage oflight.

In the light emitting device 3, the polarization direction differsbetween the light from the first semiconductor laser element 20 and thelight from the second semiconductor laser elements 30 by 90 degrees. Forexample, the first semiconductor laser 20 emits a p-polarized laserbeam, and the second semiconductor laser elements emit a s-polarizedlaser beam from the respective emission end surfaces, Accordingly,allowing the light emitted from the first semiconductor laser element 20to pass through the waveplate 300 can align the polarization directionof the light beams from the first and second semiconductor laserelements 20 and 30 exiting from the light emitting device 30.Accordingly, the waveplate 300 can be any that can eliminate thepolarization direction misalignment.

According to the light emitting device 3 of the third embodiment, alight emitting device can be provided in which the polarizationdirections of the light beams emitted from the first and secondsemiconductor laser elements can be aligned before the beams are output.

By providing a waveplate 300 on the surface of the lens member 280opposing the surface where the lens parts 282 are disposed as in thecase of the light emitting device 3, a compact design light emittingdevice 3 capable of outputting light with aligned polarization directioncan be produced. Because the structure of the light emitting device 3allows collimated light to enter the waveplate 300, reflection loss atthe surface of the waveplate 300 can be reduced as compared to caseswhere dispersed or collected light is allowed to enter.

Fourth Embodiment

A light emitting device according to a fourth embodiment will beexplained. next. It is similar to the light emitting device 3 accordingto the third embodiment in terms of having constituent elements such asa base, a single first semiconductor laser element, two secondsemiconductor laser elements, two light reflecting members, a submount,a cover member, a lens member, bonding parts, wires, and a waveplate. Onthe other hand, it differs from the light emitting device 3 of the thirdembodiment in terms of the surface on which the lens member is disposed,the shape of the waveplate, the manner in which the lens member isbonded to the waveplate, and the shape of the light reflecting surfaceof the first light reflecting member.

FIG. 20 is a perspective view of the light emitting device 4 viewed fromthe side from which light exits. FIG. 21 is a top view of the lightemitting device 4 shown in FIG. 20 assuming that the surface from whichlight exits is the upper surface. FIG. 22 is a cross-sectional view ofthe light emitting device 4 taken along line XXII-XXII in FIG. 21 . FIG.23 is a perspective view of the light emitting device 4 visualizing thespace where the semiconductor laser elements are disposed by removing aportion of the structure when viewed in the same direction as in FIG. 20.

In the light emitting device 4, the lens member 280 is disposed suchthat the lens parts 282 of the lens member 280 are positioned on thesurface opposing the surface that is bonded to the cover member 70. Thatis, the lens member 280 is positioned such that the three lens parts 282are on the opposite side of the side that is closer to the upper surfaceof the cover member 70. Furthermore, the upper surfaces lens surfaces)of the three lens parts 282 surface up relative to the lens member 280disposed above the base 10.

The lens member 280 is bonded to the cover member 70 via bonding parts90 on the cover member 70. That is, the lower surface of the lens member280 and the upper surface of the cover member 70 are bonded via anadhesive which forms the bonding parts 90. This allows the light beamsemitted from the first and second semiconductor laser elements to enterthe non-lens part 281 of the lens member 280 before being output fromthe lens parts 282 of the lens member 280.

In the light emitting device 4, when viewed while considering therecessed side of the non-lens part 281 as the upper surface side and theopposing flat surface as the lower surface side, the upper surface sideof the lens member 280 is located on the upper surface side of the lightemitting device 4 without turning the lens member 80 upside down as inthe case of the light emitting device 3.

The three lens parts 282 of the lens member 280 are positioned toindividually correspond to the semiconductor laser elements disposed onthe bottom part of the base 10. That is, the upper surfaces (i.e., lenssurfaces) of the three lens parts 282 become the surfaces from which thelight beams of the three semiconductor laser elements passing throughthe lens member 280 are output.

The waveplate 400 is disposed to change the polarization direction ofthe light emitted from the first semiconductor laser element 20. Thewaveplate 400 is disposed on the lens member 80. The waveplate 400 ispositioned on the surface on the side where the recess is formed in thelens member 280. In other words, the surface on the recessed side.

The waveplate 400 is disposed above the first lens part 283 of the lensmember 280 in the region through which the light of the firstsemiconductor laser element 20 exiting from the first lens part 283passes.

This allows the light emitted from the first semiconductor laser element20 which enters the non-lens part 281 of the lens member 280 and exitsfrom the first lens part 283 of the lens member 280 to enter thewaveplate 400.

In the light emitting device 4, the waveplate 400 is bonded to the uppersurface of the recessed non-lens part 281. More specifically, thewaveplate 400 is bonded to the uppermost surface of the lens member 280which is a recessed structure. In order to avoid contact between thewaveplate 400 and the first lens part 283, at least, the distance (i.e.,height) from the bonding surface between the lens member 280 and thecover member 70 to the first lens part 283 is preferably designed so asat least not to exceed the distance (i.e., height) from the bondingsurface between the lens member 280 and the cover member 70 to thebonding surface between the recessed non-lens-part 281 and the waveplate400.

To be bonded to the upper surface of the recessed non-lens member 281,the waveplate 400 is formed into a shape that can secure the portion tobe bonded to the non-lens member 281. The waveplate 400 in the lightemitting device 4 has a bonding portion bonded to the upper surface ofthe recessed non-lens part 281 and a non-bonding portion extending inthe direction toward the first lens part 283 from the bonding portion.

This manner of bonding can eliminate a concern that the adhesiveintrudes the beam passing region between the lens member 280 and thewaveplate 400, thereby simplifying the mounting process.

The non-bonding portion is preferably not in contact with the first lenspart 283. If in contact, the tolerances in forming the lens shape of thefirst lens part 283 can affect the mounting accuracy of the waveplate400. The light output from the first lens part 283 of the lens member280 enters and passes through the non-bonding portion of the waveplate400. From a perspective of reduction in a light emitting device size,the waveplate 400 preferably fits within the outline of the lens member280 in a top view.

The bonding portion of the waveplate 400 is the same size as, or largerthan, the non-bonding portion. In order for more secure bonding of thewaveplate, the waveplate 400 and the lens member 280 are preferablydesigned such that the bonding portion is larger. That is, the outlineof the bonding surface of the lens member 280 is designed to be largerthan the outline of the first lens part 283 when viewed from above. Thebonding portion may be smaller than the non-bonding portion, but asmaller bonding portion can lead to unstable bonding.

The bonding surface of the recessed non-lens part 281 to be bonded tothe waveplate 400 is provided on the side of the first lens part 283along the direction of linking the first to third lens parts (i.e., thelinking direction). When viewed from above, the bonding surface of thenon-lens part 281 is located such that the first lens part 283 isinterposed between the bonding surface of the non-lens part 281 and thesecond lens part 284.

In the light emitting device 4, the shape of the light reflectingsurface of the first light reflecting member 450 is flat, but notcurved. Similar to the first light reflecting member 450, the secondlight reflecting member 60 has a flat light reflecting surface.Employing a fiat surface instead of a curved surface brings the positionCP1 irradiated by the central ray of the first semiconductor laserelement 20 closer to the position CP2 irradiated by the central ray ofthe second semiconductor laser element 30.

Similar to the first embodiment, the angle formed by the flat lightreflecting surface and the bottom surface of the first light reflectingmember 450 can be determined to allow the light to be more efficientlycollimated at the spot where the light is collimated by the lens member280. Accordingly, depending on the situation, the angle can be differentfrom, or the same as, that set for the second light reflecting member60.

Fifth Embodiment

A light emitting device 5 according to a fifth embodiment will beexplained next. The constituent elements of the light emitting device 5is similar to the light emitting device 4 according to the fourthembodiment in terms of including a base, a single first semiconductorlaser element, two second semiconductor laser elements, a submount, alight reflecting member, a cover member, a lens member, bonding parts,wires, and a waveplate. On the other hand, the light emitting device 5differs from the light emitting device 4 according to the fourthembodiment in terms of the shape of the lens member, the shape of thewaveplate, the manner in which the lens member is bonded to thewaveplate, and the number of light reflecting members.

FIG. 24 is a perspective view of the light emitting device 5 viewed fromthe side from which the light exits. FIG. 25 is a top view of the lightemitting device 5 shown in FIG. 24 assuming that the side from whichlight exits is the upper surface. FIG. 26 is a cross-sectional view ofthe light emitting device 5 taken along line XXVI-XXVI in FIG. 25 . FIG.27 is a perspective view of the light emitting device 5 visualizing thespace where the semiconductor laser elements are disposed by removing aportion of the structure when viewed in the same direction as in FIG. 24.

In the light emitting device 5, the recessed non-lens part 581 of thelens member 580 is formed to surround the lens parts 582. The recessedstructure is formed such that upper surface portions on both sides ofthe first lens part 583 face the first lens part 583 in the non-linkingdirection, in addition to the direction of linking the first to thirdlens parts (i.e., the linking direction). The non-linking directionmeans the direction along which one lens part 582 is not linked toanother lens part 582. That is, a straight line drawn in the linkingdirection intersects with only one lens part 582.

In the light emitting device 5, the waveplate 500 is bonded to the uppersurface portions of the recessed structure located on both sides of thefirst lens part 583 in the non-linking direction. The bonding surfaceportions of the non-lens part 581 are located to interpose the firstlens part 583 when viewed from above. The waveplate, on the other hand,does not contact the portions of the upper surface of the recessedstructure located in the linking direction. It may be bonded to theportions that include one located in the linking direction.

The waveplate 500 has a first bonding portion which is bonded to theupper surface of the recessed non-lens part 581 on one side, anon-bonding portion extending from the bonding portion toward the firstlens part 583, and a second bonding portion which is bonded to the uppersurface of the recessed non-lens part 581 on the other side of thenon-bonding portion.

According to this mariner of bonding, the waveplate 500 can be fixed ina more stable manner because it is bonded to the lens member at twolocations spanning over the first lens part 583.

In the light emitting device 5, moreover, a single light reflectingmember (i.e., the first light reflecting member 550) forms the lightreflecting surface to reflect the light beams from the first and secondsemiconductor laser elements. The shape of the light reflecting surfaceis flat. The shape of the light reflecting surface may be curved.Constructing the light reflecting surface using a single first lightreflecting member makes the beam path length to the position CPIirradiated by the central ray of the first semiconductor laser element20 the same as the beam path lengths to the positions CP2 irradiated bythe central rays of the second semiconductor laser elements 30.

Based on the light emitting devices 3 to 5 of the third to fifthembodiments explained above, at least the light emitting devicesdescribed below are disclosed.

A light emitting device includes a base having a bottom part, a firstsemiconductor laser element disposed on the bottom part of the base, oneor more second semiconductor laser elements, a lens member, and awaveplate. The one or more second semiconductor laser elements arcdisposed on the bottom part of the base and each having a differentpolarization direction from that of the first semiconductor laserelement. The lens member is a member into which the light beams from thefirst and second semiconductor laser elements enter.

The waveplate is disposed on the lens member to change the polarizationdirection of the light from the first semiconductor laser element.

In the light emitting device described above, the waveplate is disposedin the region through which the light from the first semiconductor laserelement entering the lens member passes.

The above described lens member is formed with a recess. The lens memberhas one or more lens parts each having a lens shape and a non-lens partwhere the one or more lens parts are disposed in the recess.

The waveplate described above is disposed on the surface opposing therecessed-side surface of the lens member. The light from the firstsemiconductor laser element enters the lens part of the lens member,exits from the non-lens part of the lens member, and enters thewaveplate.

The above described lens member is disposed above the base such thatlens surfaces of the lens parts having lens shapes face down. Thewaveplate is disposed on the upper surface side of, and bonded to, thelens member.

The above described waveplate is disposed on the recessed-side surfaceof the lens member. Time light from the first semiconductor laserelement enters the non-lens part, exits from the lens part of the lensmember, and enters the waveplate.

The above described waveplate is disposed on the uppermost surface ofthe recessed lens member.

The above described lens member is disposed above the base such that thelens surfaces of the lens parts face up. The waveplate is disposed onthe upper surface side of, and bonded to, the lens member.

The above described light emitting device further includes a covermember bonded to the base to seal the space in which the first andsecond semiconductor laser elements are disposed. The lens member isbonded to the cover member.

Design Example 1

A specific design example of the light emitting device according to thefirst embodiment will be described next. A red light emitting firstsemiconductor laser element having a vertical beam divergence angle ofabout 65 degrees, a green light emitting second semiconductor laserelement having a vertical beam divergence angle of about 46 degrees, anda blue light emitting second semiconductor laser element having avertical beam divergence angle of about 45 degrees are disposed on thebottom part.

The distance from the submount provided with the first and secondsemiconductor laser elements to the first and second light reflectingmembers is 0.15 mm. The height from the surface of the base on which thesubmount is disposed to the cover member is 1.00 mm. The height from thesurface of the base on which the submount is disposed to the surface ofthe submount on which the first and second semiconductor laser elementsare disposed is 0.40 mm. The height from the surface of the base onwhich the first light reflecting member is disposed to the lightreflecting surface is 0.16 mmm at minimum and 0.85 mm at maximum, Theheight from the surface of the base on which the second light reflectingmember is disposed to the light reflecting surface is 0.25 mm at minimumand 0.80 mm at maximum. The thickness of the cover member (i.e., theheight from the bottom surface to the upper surface of the cover member)is 0.50 mm. The thickness of the bonding parts is 0.2 mm. The thicknessof the non-lens part of the lens member (i.e., the height from thebottom surface of the lens member to the interface with the lens parts)is 1.40 mm. The thickness of each lens part (i.e., the height from theinterface with the non-lens part to the vertex of the lens shape) is 0.3mm. The lens width of each of the first to third lens parts of the lensmember is 1.20 mm.

The distance from the emission end surface of the first semiconductorlaser element to the position on the light reflecting surface irradiatedby the central ray from the first semiconductor laser element is 0.47mm. The distance from the end surface of each second semiconductor laserelement to the position on the light reflecting surface irradiated bythe central ray from the second semiconductor laser element is 0.30 mm.The beam divergence angle of he reflected light of the first lightreflecting member in the vertical direction is 8.3 degrees.

In such a light emitting device, assuming that the width correspondingto the major diameter is 1.0 mm, the collimated light output from thelens member was calculated to have 90% or more of the light emitted froma semiconductor laser element in that width.

The present disclosure has been described above. The light emittingdevices according to the present invention having the technical featuresdisclosed in the description herein are not limited to the structures ofthe light emitting devices 1 to 5 explained with reference to theseembodiments. For example, the present invention is applicable to a lightemitting device having a constituent not disclosed in any of theembodiments. As such, the mere fact that there is a difference from thedisclosed light emitting devices would not provide any ground for theinapplicability of the present invention.

It goes without saying that, even in the case where a light emittingdevice according to one embodiment which includes a modified element byincorporating, or replacing with, a part of the constituents disclosedin another embodiment, so long as such a modification is merely a matterof design choice for a person of ordinary skill in the art, the devicewould essentially fall within the scope of the present invention.

In other words, the present invention is applicable to a device even ifit is not essential for the device to necessarily and fully include allof the constituent elements of the light emitting device disclosed byany of the embodiments. For example, in the event that a certainconstituent element of a light emitting device disclosed by any of theembodiments is not disclosed in the claim scope, we claim theapplicability of the invention disclosed in the claim scope byrecognizing the design flexibility for a person of ordinary skill in theart for such a constituent through the use of an alternative, anomission, a shape change, a change in the materials employed, or thelike, without limiting it to what is disclosed in the embodiment.

The light emitting devices described in the embodiments of the presentinvention can be used as light sources for head-mounted displays,projectors, automotive headlights, lighting fixtures, displaybacklights, and the like.

What is claimed is:
 1. A light emitting device comprising: a base havinga bottom part; a first semiconductor laser element disposed on thebottom part of the base; a second semiconductor laser element disposedon the bottom part of the base, the second semiconductor laser elementhaving a different polarization direction from a polarization directionof the first semiconductor laser element; a lens member into which lightbeams from the first semiconductor element and the second semiconductorlaser element enter, the lens member having a lower surface joined withthe base and a lens surface, the lens surface being positioned so as notto protrude toward the bottom part of the base beyond the lower surface;and a waveplate configured to change the polarization direction of lightfrom the first semiconductor laser element, wherein the base has a framepart forming a lateral surface surrounding the first semiconductor laserelement and the second semiconductor laser element, the base supportsthe lens member and the waveplate, the lens member has a first lenspart, a second lens part and a non-lens part, each of the first lenspart and the second lens part having a lens shape and respectivelycorresponding to the first semiconductor laser element and the secondsemiconductor laser element, the non-lens part defines a recess, and thefirst lens part and the second lens part are disposed in the recess ofthe non-lens part, and a lower surface of the waveplate is positioned ona surface of the lens member on a side where the recess is defined. 2.The light emitting device according to claim 1, wherein the first lenspart and the second lens part are arranged to respectively collimate thelight from the first semiconductor laser element and the secondsemiconductor laser element.
 3. The light emitting device according toclaim 1, further comprising a third semiconductor laser element disposedon the bottom part of the base, wherein the first semiconductor laserelement, the second semiconductor laser element, and the thirdsemiconductor laser element are arranged side by side, and the firstsemiconductor laser element is arranged at one end among the firstsemiconductor laser element, the second semiconductor laser element, andthe third semiconductor laser element.
 4. The light emitting deviceaccording to claim 1, further comprising a cover member bonded to thebase, wherein the lens member is bonded to the cover member, and thewaveplate covers an emission end surface of the first semiconductorlaser element in a top view.
 5. The light emitting device according toclaim 1, wherein the waveplate covers the first lens part in a top view,and the waveplate does not cover the second lens part in the top view.6. The light emitting device according to claim 1, wherein a long-sidelength of the waveplate in a top view is the same as, or greater than, along-side length of the first lens part in the top view, and ashort-side length of the waveplate is the same as, or greater than, ashort-side length of the first lens part in the top view.
 7. The lightemitting device according to claim 1, wherein the waveplate has abonding portion bonded to an upper surface of the non-lens part on theside where the recess is defined, and the waveplate has a non-bondingportion extending in a direction toward the first lens part from thebonding portion.
 8. The light emitting device according to claim 7,wherein the bonding portion of the waveplate is the same size as, orlarger than, the non-bonding portion.
 9. A light emitting devicecomprising: a base having a bottom part; a first semiconductor laserelement disposed on the bottom part of the base; a second semiconductorlaser element disposed on the bottom part of the base, the secondsemiconductor laser element having a different polarization directionfrom a polarization direction of the first semiconductor laser element alens member into which light beams from the first semiconductor elementand the second semiconductor laser element enter, the lens member havinga lower surface joined with the base and a lens surface, the lenssurface being positioned so as not to protrude toward the bottom part ofthe base beyond the lower surface; and a waveplate configured to changethe polarization direction of light from the first semiconductor laserelement, wherein the base has a frame part forming a lateral surfacesurrounding the first semiconductor laser element and the secondsemiconductor laser element, the base supports the lens member and thewaveplate, the lens member has a first lens part, a second lens part anda non-lens part, each of the first lens part and the second lens parthaving a lens shape and respectively corresponding to the firstsemiconductor laser element and the second semiconductor laser element,the non-lens part defines a recess, and the first lens part and thesecond lens part are disposed in the recess of the non-lens part, andthe waveplate has a first bonding portion which is bonded to an uppersurface of the non-lens part on a side where the recess is defined, anon-bonding portion extending from the bonding portion toward the firstlens part, and a second bonding portion which is bonded to the uppersurface of the non-lens part on the other side of the non-bondingportion.
 10. The light emitting device according to claim 1, furthercomprising a cover member having a lower surface bonded to the base andan upper surface bonded to the lens member, wherein the lens member isjoined with the base via the cover member.